Prevention of Proliferative Vitreoretinopathy by HC-HA/PTX3 Summary Proliferative vitreoretinopathy (PVR) is characterized by membranes that develop on the surface of the retina after rhegmatogenous retinal detachments (RRD), during which time RPE cells are dispersed into the vitreous cavity where they lose contact inhibition and are exposed to multiple growth factors and cytokines. This pathological setting promotes proliferation and EMT of RPE cells to fibroblasts or myofibroblasts that produce intravitreal membranes. These PVR membranes exert tractional forces on the retina and become the leading cause of failure after RRD surgery. Despite additional surgical interventions, the visual outcome still remains poor. Prevention of PVR during the initial RRD surgery could improve the visual success rate. Unfortunately, all previous attempts using different agents have been unsuccessful. Using an in vitro RPE cell culture model, we have reported that following perturbation of contact inhibition of RPE cells, EGF and FGF-2 upregulate while TGF-?1 downregulates canonical Wnt signaling in the proliferative phase, but TGF-?1 promotes canonical TGF-?/Smad/ZEB signaling in the irreversible scarring phase of EMT. We have successfully purified and characterized HC-HA/PTX3 from amniotic membrane (AM) and have reported that this unique matrix is responsible for AM's anti-inflammatory, anti-scarring and anti- angiogenic therapeutic actions. HC-HA/PTX3 is formed by tight association between pentraxin 3 (PTX3) and HC-HA, which consists of high molecular weight hyaluronic acid (HA) covalently linked to heavy chain 1 (HC1) of inter-?-trypsin inhibitor (I I) through the catalytic action of tumor necrosis factor-stimulated gene-6 (TSG-6). Through Phase I support, we have proven the concept that HC-HA/PTX3 can be a novel ?biologic? to prevent PVR by inhibiting proliferation and EMT in the aforementioned in vitro model that has been optimized to better mimic in vivo pathological processes of PVR regarding cell density, growth factor stimulation, and measurement methods. We have developed the potency assay that is required as an in-process control of the manufacturing of HC-HA/PTX3 from different donors, demonstrated the safety (i.e., lack of cytotoxicity) and the efficacy of HC- HA/PTX3 over a wide range of doses, demonstrated the efficacy of HC-HA/PTX3, but not HA, in inhibiting proliferation and gel contraction caused by both ARPE-19 cells and primary human RPE cells, and delineated the mode of action of HC-HA/PTX3 in inhibiting the aforementioned Wnt and TGF-? signaling. These accomplishments allow us to propose in this Phase II application to scale up the manufacturing of HC-HA/PTX3 by combining AM and umbilical cord (UC) from the same donor (Aim 1), to establish the release criteria and the stability of the HC-HA/PTX3 formulation via reproducible GMP manufacturing (Aim 2), and to determine the safety and efficacy of intravitreal injection of HC-HA/PTX3 in our recently-established rabbit PVR model (Aim 3). Collectively, we would like to gather necessary and sufficient pre-clinical data for an IND submission to the FDA so that the Company can capture a unique business opportunity by deploying this novel biologic to fulfill the unmet global need of treating this severe retinal blinding disease.